What is the council supposed to do now that they have taken control of my landlord's dangerous property?

Because the council placed an interim management order on your building on the 10th of last month, they are now bound by specific duties under the Housing Act 2004. First, the council has a duty to address your immediate safety concerns. The law states the authority must "take any immediate steps which they consider to be necessary for the purpose of protecting the health, safety or welfare of persons occupying the house" [cite:uk-housing-act-2004-sec106]. This means that because you are facing a broken boiler and spreading mould, the council is required to act as soon as is practical to ensure your health and safety are not at risk. Second, the council is responsible for the day-to-day running of the building while they decide whether to grant the landlord a licence or take over permanently. They must "take such other steps as they consider appropriate with a view to the proper management of the house" [cite:uk-housing-act-2004-sec106]. This includes making sure the building is looked after properly during this transition period. Regarding your fear about fire or leaks, the law specifically addresses insurance. The council's duty includes "taking such steps as are necessary to ensure that, while the order is in force, reasonable provision is made for insurance of the house against destruction or damage by fire or other causes" [cite:uk-housing-act-2004-sec106]. This means the council must ensure there is insurance coverage in place to protect the property from major disasters. While the council has these duties, the law does not set a specific number of days by which they must finish a repair. It only says they must act "as soon as practicable" [cite:uk-housing-act-2004-sec106]. Therefore, it is uncertain exactly how quickly they will fix your specific boiler or mould issue, as they decide what steps are "necessary" or "appropriate."